An essential property of elevators and other conveying means for transporting people and goods is reliability of operation. To ensure reliability of operation, various maintenance programs are employed. Maintenance programs are designed to maintain a maximal working capacity of conveying means.
In the following, a maintenance program type that can be used e.g. for elevators is presented by way of example. In determining an appropriate maintenance program, many factors have to be taken into account: manufacturer, elevator type, history data, operating environment, volume of utilization, etc. The maintenance program for an elevator in heavy and frequent use may differ very much from the maintenance program for an elevator in a low-rise apartment house where the elevator is not much used. In the former case, the maintenance program may define maintenance work for each month of the year, whereas in the latter case one or two yearly maintenance visits according to the maintenance program may be sufficient.
A possible maintenance program concept is of a modular nature. In a modular maintenance program, several maintenance modules differing from each other in content are defined, and these modules are executed at predetermined intervals of time. FIGS. 1a, 1b and 1c present an example of application of a modular maintenance program concept. In the figures, the horizontal axis represents time (month). In this example, the maintenance program for the maintenance object comprises four maintenance modules (I, II, III and IV) differing from each other in respect of content. In FIG. 1a, the maintenance program begins in January, in FIG. 1b in February and in FIG. 1c in December. In other words, the periodic schedule of execution of different maintenance modules is the same in each figure, only the starting month of the maintenance program varies. An example of the principle of modular maintenance program is described in specification U.S. Pat. No. 6,330,935.
For each maintenance module, an estimate of the required amount of work can be determined. The actual maintenance work is carried out by a serviceman whose maintenance domain includes the maintenance module in question.
The maintenance modules (i.e. maintenance tasks included in the maintenance module) can be allocated to each serviceman according to whose domain the maintenance module pertains to. A difficulty in allocation is e.g. the fact that, for instance on an annual scale, there may be as many as 100-300 separate maintenance units pertaining to one serviceman in his own domain. Further, each serviceman generally has a monthly capacity, which indicates the planned amount of work that the serviceman can perform during each month. When the above-described modular maintenance program concept is used, it is required that the starting months of the maintenance programs be so adjusted that the serviceman will be able to perform the maintenance tasks in his domain during each month. In short, the work allocator should be able to allocate maintenance modules to servicemen in such a way that the modules will be executed on time and that each serviceman is not allocated too much or too little maintenance work in individual months. At the same time, the work allocator should be able to maximize the amount of maintenance work to be performed within the limits of the working capacity of each serviceman.